class Commit implements Serializable:
    // Constructor
    public Commit(String parentId, String message)

    // Fields
    /** The SHA-1 identifier of my parent, or null if I am the initial commit. */
    private final String parent;
    /** My log message. */
    private final String message;
    /** My timestamp. (java.util.Date) */
    private Date commitDate;
    /** A mapping of file names to the SHA-1's of their blobs. */
    private HashMap<String, String> contents = new HashMap<>();
    
    // Methods
    public String toString()
    /** Get SHA-1 identifier of my parent, or null if I am the initial commit. */
    String getParent()
    /** Finalize me and write me to my repository. */
    void finalize()
    /* Assorted getters and setters for contents and other fields excluded.
       Methods supporting merge also excluded. */
    .
    .
    .